The present invention is directed to a piezo actuator that comprises an electrically conductive contact lug for electrical contacting of an electrode. An employment of such a piezo actuator is also recited.
A piezo actuator is usually constructed of a plurality of piezo elements arranged to form a stack-shaped actuator member. Each piezo element is composed of a piezo ceramic layer that is provided with a metallic electrode at both sides. When an electrical voltage is applied to these electrodes, then the piezo ceramic layer reacts with a lattice distortion. As a result thereof, the piezo element expands and contracts and, thus, the actuator member expands and contracts in a direction that is determined by the arrangement of the piezo ceramic layer and of the electrodes of a piezo element. A usable modification of an expansion of a stack-shaped actuator member occurs according to an extent of the expansion and contraction.
German reference DE 197 15 488 discloses such a piezo actuator. The piezo actuator has an actuator member with a multi-layer structure comprising at least one stack of alternating electrode and piezo ceramic layers. One electrode layer serves neighboring piezo ceramic layer as electrode. To that end, an electrical contacting of the electrode layers ensues in an alternating polarity. The alternating polarity is achieved with the assistance of two metallization strips that are laterally applied to the actuator member. A metallization strip extends over a height that derives from electrically active layers of the actuator member stacked on top of one another. One of the metallization strips is electrically conductively connected to each second electrode layer and is insulated from each first electrode layer lying therebetween. By contrast thereto, the second metallization strip is insulated from every second electrode layer and electrically conductively connected to each first electrode layer.
In order to ensure the electrical contacting of every individual electrode layer, a voltage supply to a metallization strip in the known piezo actuator ensues via a strip-shaped, electrically conductive contact lug in the form of a plastic film laminated with copper. The contact lug is thereby soldered to a metallization strip via one of its edges. The contact lug likewise extends over the entire height of the electrically active layer of the actuator member. An outside edge of the contact lug pointing away from the actuator member is connected to a rigid electrical terminal element. A crack in a metallization strip that potentially occurs is electrically bridged with the assistance of the contact lug. As a result thereof, the piezo actuator exhibits a high plurality of cycles and, thus, a high service life. One cycle comprises a one-time expansion and contraction of the piezo actuator or, respectively, of the actuator member in a specific direction.